1. Field of the Invention
This invention relates generally to woodworking equipment and, in particular, to an apparatus for automatically positioning the center of a work-piece in exact alignment with the center of a cutting tool, such as a router bit or drill bit.
2. Background Art
In various fields of craftsmanship, there is the need for precision positioning of work-pieces so that they are positioned correctly for subsequent performance of procedures thereon; procedures such as shaping, cutting, boring, milling, and the like. In precision woodworking, it has been customary to employ guiding apparatus such as those disclosed in U.S. Pat. Nos. 4,793,604 and 5,195,730 granted to Christopher L. Taylor on Dec. 27, 1988 and Mar. 23, 1993, respectively. Those apparatus, known as INCRA.RTM. Universal Precision Positioning Jigs, embody a number of features, including a positive interlocking saw-tooth rack construction that provide adjustment in discrete increments. Overall work-piece positioning accuracy and repeatability using this approach can be very high, and is limited only by the accuracy with which the positioning rack elements can be manufactured. The availability of this high level of accuracy make it possible for INCRA.RTM. Positioning Jigs to perform certain woodworking operations which previously required special purpose jigs, fixtures, or other devices to achieve satisfactory results.
One of many such commonly performed operations is the formation of woodworking "joints" such as box joints and dovetail joints (usually with a rotating router bit in a router table) which are used to join two boards securely together in a close-fitting interlocking relationship, most often at right angles to each other. Such a precise fit results in a joint that is not only suitably strong, but also one that is visually appealing. Another requirement for a visually appealing joint is that the cuts forming the joint are located symmetrically about the ends of the two boards which are being joined together. Such symmetry also insures that both the top and bottom edges of the two boards will be flush with each other when the final fit is achieved.
The attainment of symmetry in woodworking joints requires an initial setup procedure commonly known as "centering." A work-piece is properly centered when the guiding apparatus (such as the INCRA.RTM. Positioning Jig) is located relative to the cutting tool in such a manner that when one edge of the work-piece to be centered is abutted against the guiding apparatus, the center of said work-piece will be aligned with the center of the cutting tool (such as a router bit or drill bit).
The procedure for establishing this initial centered relationship between work-piece, cutting tool, and guiding apparatus has heretofore been carried out manually, normally requiring one or more stages of "trial-and-error" testing. Not only is such an approach complicated and time consuming, but it is also wasteful of wood or other work-piece materials.
From the foregoing, it will be appreciated that what is needed in the art is an apparatus for centering a work-piece, which provides simple procedures for accurate, automatic centering for a wide range of work-piece widths.